The invention relates to a device and a method for influencing the operating mode of at least one vehicle stabilizing device which is arranged in a vehicle.
Vehicle stabilizing devices are known nowadays in a wide variety of forms. Examples of these are brake assistants (BAS), brake slip controllers (ABS), traction slip controllers (ASR), electronic traction systems (ETS) or vehicle movement dynamic controllers (ESP). These vehicle stabilizing devices have one thing in common: they actuate, independently of the driver, at least brake actuators which are assigned to the vehicle wheels, in order to stabilize the vehicle. These vehicle stabilizing devices have proven effective in the road mode. They contribute to better control of vehicles and to reducing accidents.
Against this background it is understandable that, if possible, a large proportion of the vehicles taking part in road traffic should be equipped with such vehicle stabilizing devices. This also applies to vehicles with all-wheel drive or off-road vehicles because the advanced possibilities of the vehicle stabilizing devices specified above should also be made available in these vehicles. Finally, it is desirable to make road traffic as safe as possible and to reduce the risk of accidents as far as possible.
In vehicles with all-wheel drive, to be more precise in off-road vehicles in which the long-proven mechanical locks are used for hard or extreme off-road use, which is referred to as the off-road mode, problems may occur if the vehicle is operated with the mechanical locks activated and one of the vehicle stabilizing devices specified above actuates, independently of the driver, one of the brake actuators assigned to the vehicle wheels during such an operating state of the vehicle, that is to say a braking intervention which is independent of the driver is carried out. These aforesaid off-road vehicles have three mechanical differential locks. As a result, when differential locks are activated, one hundred percent mechanical coupling of the front and rear axle differentials are ensured and furthermore the front and the rear axles are also mechanically coupled by means of the differential lock in the transfer gear. If the braking intervention which is independent of the driver is carried out in the case of such a mechanical coupling of the axles, this leads to the braking forces being displaced via the axles which are now “rigid”. In other words, the braking force is not only generated at the one vehicle wheel whose brake actuator is actuated, but also at the other vehicle wheels owing to the “rigid” axles. This leads to an undesired vehicle behavior.
The prior art discloses various devices which are concerned with the problems described above.
For example, German document DE 196 41 101 A1 discloses a method for controlling a longitudinal lock of an all-wheel-driven vehicle. In order to bring about better driving comfort, the longitudinal lock is automatically closed when there is a load change. However, apparatuses such as an antilock brake system or a vehicle movement dynamic system are preferred in order to ensure undiminished driving stability and braking stability of the vehicle. That is to say, when the chassis control or brake control is actuated, the longitudinal lock is not taken into account, with respect to the load change. Moreover, when there is a braking operation initiated by the driver of the vehicle, if the longitudinal lock is closed, it is opened immediately. In summary, the following can be inferred from German document DE 196 41 101 A1: if a braking intervention which is dependent on a driver or a braking intervention which is independent of a driver is to be carried out, this braking intervention is given priority and the longitudinal lock is opened up or even not closed in the first place.
European document EP 0 191 131 B1 is further prior art. In this document, a road vehicle is proposed with an antilock protection in which the front wheels are controlled individually and the rear wheels are controlled according to the select-low principle. The driven rear axle is provided with a differential lock which can be switched on. In order to increase the stability of the vehicle when the differential lock is engaged, an apparatus is provided which detects the engagement of the lock and, when the lock is engaged, switches over the logic of the antilock protection electronic system of the front axle from individual control (IR) to a modified individual control (MIR), a select low control (SLR) or some other control logic which attenuates the yaw moment and steering torque, at the front wheels. From European document EP 0 191 131 B1 which is to be considered as forming the generic type, the following can thus be inferred: the operating mode of a vehicle stabilizing device which actuates, independently of the driver, at least brake actuators which are assigned to the vehicle wheels, in order to stabilize the vehicle, is influenced in terms of its operating mode as soon as the longitudinal lock assumes an operating state other than the non-switched operating state.
The vehicle which is described in European document EP 0 191 131 A1 is only equipped with a vehicle stabilizing device, specifically with an antilock protection device. Proposals as to what procedure should be adopted if the vehicle is equipped with a plurality of vehicle stabilizing devices which actuate, independently of the driver, at least brake actuators which are assigned to the vehicle wheels, in order to stabilize the vehicle, are not given in this document.
Against this background, the following object presents itself: the intention is to provide a device which, in vehicles with all-wheel drive or in off-road vehicles which are equipped both with differential locks and with vehicle stabilizing devices which actuate, independently of the driver, at least brake actuators which are assigned to the vehicle wheels, in order to stabilize the vehicle, allows an unrestricted off-road mode of these vehicles, while simultaneously supporting the driver for as long as possible in critical driving situations which may possibly occur.
Unrestricted off-road mode is to be understood to mean the following: a vehicle with all-wheel drive or an off-road vehicle which is equipped with vehicle stabilizing devices, which actuate, independently of the driver, at least brake actuators which are assigned to the vehicle wheels, in order to stabilize the vehicle, despite the presence of the vehicle stabilizing devices is to behave—in the off-road mode with the locks activated—like a vehicle which does not have such vehicle stabilizing devices and in which, consequently, no adverse effects of the vehicle behavior as a result of braking interventions which are independent of the driver can occur during the off-road mode.
This object is achieved by means of claimed features.
According to the invention, in order to achieve the above object in a vehicle in which a plurality of vehicle stabilizing devices which operate according to different strategies are arranged which actuate, independently of the driver, at least brake actuators which are assigned to the vehicle wheels, in order to stabilize the vehicle, and which is equipped with at least one switchable, in particular mechanical, differential lock in the power train, which differential lock assumes a non-switched operating state, and in addition to this non-switched operating state a first operating state which is different from the non-switched operating state and in which the differential lock is preselected, and a second operating state which is different from the non-switched operating state and the first operating state and in which the differential lock is switched, as soon as the differential lock assumes the first operating state, some of the vehicle stabilizing devices are influenced in terms of their operating mode, and as soon as the differential lock assumes the second operating state, all the vehicle stabilizing devices are influenced in terms of their operating mode.
This procedure according to the invention, which corresponds to a stepped procedure, has the following advantage: as long as the differential lock is in the non-switched operating state, there is no rigid coupling between the wheels of a vehicle axle or between the axles of the vehicle, and consequently braking forces which are increased at a wheel cannot be transmitted to other wheels. This means that the brake actuators which are assigned to the vehicle wheels cannot be actuated appropriately for requirements without there being the risk of disruptive effects occurring in the process. There is no need to influence the vehicle stabilizing devices in their operating mode, and consequently their entire functionality is available to support the driver. In contrast, as soon as the differential lock is in the preselected operating state, i.e. in the transition phase between the non-switched operating state and the switched operating state, it can be assumed that within a foreseeable time a rigid coupling may occur between the individual wheels or axles, thus displacing braking forces between the individual wheels. Although, in the preselected operating state, the differential lock is not yet activated, its activation will take place within a short time period. In order to prevent a possibly occurring, disruptive displacement of braking forces, some of the vehicle stabilizing devices are already influenced at this stage in terms of their operating mode. This is a preventative measure, since the time at which the differential lock is activated last and it becomes necessary to influence the vehicle stabilizing devices in terms of their operating mode cannot be determined in advance precisely. Only some of the vehicle stabilizing devices are influenced in terms of their operating mode, specifically those whose support in the transition phase and the associated vehicle state can be dispensed with. The remaining vehicle stabilizing devices are not influenced in their operating mode, and are thus available to support the driver. These are vehicle stabilizing devices whose support should not be dispensed with, even in the transition phase and the associated vehicle state. As a result, stabilization of the vehicle is ensured to a minimum degree. Only if the differential lock is in the switched operating state are the remaining vehicle stabilizing devices also influenced in their operating mode, meaning that all the vehicle stabilizing devices are made available to the driver, at any rate to an only still restricted degree or even are no longer made available. This measure avoids possible displacement of braking forces owing to the coupling between the wheels. The support to the driver by the vehicle stabilizing devices can be dispensed with in such operating states of the vehicle, there are no speeds present, since in such operating states stabilizing braking interventions which are independent of the driver are usually not necessary.
The operating mode of the vehicle stabilizing devices is advantageously influenced here in each case in such a way that the actuation—independent of the driver—of the brake actuators which are assigned to the vehicle wheels, by the respective vehicle stabilizing device does not occur. As a result, if the differential lock assumes an operating state other than the non-switched operating state, i.e. is either preselected or switched or activated, it is ensured that none of the brake actuators which are assigned to the vehicle wheels is actuated independently of the driver, and an increase in braking force or decrease in braking force does not take place at any of the vehicle wheels, which increase or decrease could give rise, in this operating state of the differential lock, to a disadvantageous effect on another vehicle wheel or another vehicle axle and would thus bring about an undesired and eventually disruptive effect on the movement of the vehicle. The advantageous effects—described above—of the respective vehicle stabilizing device corresponds to a deactivation of the respective vehicle stabilizing devices.
As already explained, with the apparatus according to the invention, the vehicle stabilizing devices are influenced incrementally in their operating mode. The following procedure advantageously presents itself: if the differential lock assumes the first operating state, with the exception of that vehicle stabilizing device which, by actuating the brake actuators independently of the driver prevents the vehicle wheels locking during a braking operation, all the vehicle stabilizing devices which are arranged in the vehicle are influenced in terms of their operating mode. As soon as the differential lock assumes the second operating state, this vehicle stabilizing device is also influenced in terms of its operating mode. This measure ensures that this vehicle stabilizing device, which is known to correspond to a brake slip controller, is made available in its full scope to the driver for as long as possible for supporting purposes.
The vehicle which has a front axle and a rear axle is advantageously a vehicle with all-wheel drive. In this vehicle, both the front axle and the rear axle are each effectively assigned a differential lock. That is to say the front axle has a differential gear mechanism with differential lock, referred to below as front axle differential gear mechanism and front axle differential lock, and the rear axle has a differential gear mechanism with differential lock, referred to below as rear differential mechanism and rear differential lock. Furthermore, in the vehicle, a further differential lock is effectively arranged between the front axle and the rear axle. In other words: the vehicle under consideration has a transfer gear, composed of a differential gear mechanism and a differential lock, for dividing the torque between the front axle and the rear axle. This differential gear mechanism and this differential lock are referred to below as longitudinal differential gear mechanism and longitudinal differential lock.
According to the invention, the operating mode of the vehicle stabilizing device is influenced as soon as the differential lock which is arranged between the front axle and the rear axle, i.e. the longitudinal differential lock, assumes an operating state other than the non-switched operating state. The influencing of the operating mode of the vehicle stabilizing device is aimed at the longitudinal differential lock for the following reason: in a vehicle with all-wheel drive which is equipped with the abovementioned three differential locks, said locks are preselected and activated in the sequence longitudinal differential lock, then rear axle differential lock and, finally, front axle differential lock. That is to say, the longitudinal differential lock is inevitably always activated irrespective of which of the three differential locks is activated last. Consequently, for the decision as to whether or not it is necessary to influence the operating mode of the vehicle stabilizing device, it is sufficient to monitor whether the longitudinal differential lock is preselected.
In a transition of the differential lock from the non-switched operating state into the switched operating state, the first operating state is assumed before the second operating state. Here, the switched operating state corresponds to the second operating state. In the non-switched operating state, the differential lock is not activated. In the switched operating state, the differential lock is activated. The first operating state which is specified above corresponds to a transition operating state between the non-switched operating state and the switched operating state.
Advantageously, at least one brake slip controller (ABS) and one brake assistant (BAS) and/or one traction slip controller (ASR) and/or one electronic traction system (ETS) and/or one vehicle movement dynamics controller (ESP) are arranged in the vehicle as vehicle stabilizing devices. In other words: the vehicle is equipped in all cases with a brake slip controller and can have any desired combination of the further vehicle stabilizing devices.
If the differential lock assumes the first operating state, i.e. is preselected, the braking assistant and/or the traction slip controller and/or the electronic traction system and/or the vehicle movement dynamics controller are influenced in their operating mode, i.e. deactivated. That is to say the brake slip controller remains uninfluenced in terms of its operating mode, as a result of which a stable vehicle behavior is ensured at least when braking occurs. Depending on which of the further vehicle stabilizing devices specified above the vehicle has, said devices are influenced, i.e. deactivated, in terms of their operating mode.
If the differential lock assumes the second operating state, i.e. is activated, in addition to the vehicle stabilizing devices whose operating mode was already influenced when the differential lock was in the first operating state, the brake slip controller is also influenced in terms of its operating mode. That is to say, the brake slip controller and the braking assistant and/or the traction slip controller and/or the electronic traction system and/or the vehicle movement dynamics controller are influenced in terms of their operating mode. In specific terms, this means: both the brake slip controller and the further vehicle stabilizing devices which are present in the vehicle are influenced in terms of their operating mode.
The operating state of the differential locks can advantageously be set by the driver by activating a switching means. The following sequence applies to the setting of the at least one further operating state of the differential locks which is different from the non-switched operating state: first, the operating state of the differential lock which is effectively arranged between the front axle and the rear axle, the longitudinal differential lock, and then the operating state of the differential lock which is effectively assigned to the rear axle, the rear axle differential lock, and then the operating state of the differential lock which is effectively assigned to the front axle, the front axle differential lock, are set.
It has proven particularly advantageous that the driver is informed about the operating state of the differential lock and/or about the operating mode of the vehicle stabilizing device which is arranged in the vehicle and/or about possibly occurring faults by means of a display means. In particular, the displaying of faults which occur at the differential locks, or which occur owing to the operation of the differential locks, is of particular interest. The monitoring of faults for the differential lock is advantageously carried out as a function at least of a signal which represents the operating state of the differential lock.
As already mentioned, the operating state of the differential lock can be set by the driver by activating a switching means. The following fault monitoring system advantageously presents itself: a fault is detected if, after activation of the switching means in order to set an operating state of the differential lock which is different from the non-switched operating state, the predefined time period has passed without the differential lock assuming this operating state.
This fault monitoring can also be improved as follows: if a first predefined time period has passed without the differential lock assuming the second operating state, a vehicle stabilizing device with which locking of the wheels is prevented during a braking operation is influenced in terms of its operating mode. In addition or as an alternative, if a second predefined time period has passed above a predefined vehicle speed without the differential lock assuming the second operating state, this situation is communicated to the driver and/or a fault entry is made in a memory medium.
It is particularly advantageous that the device according to the invention or the method according to the invention can be implemented in a simple and cost-effective way in vehicles with all-wheel drive.
Further advantages will emerge from the following description and the appended drawing. At this point it is to be noted that any desired combination of the subclaims, and thus of the subject matters described in the subclaims, are conceivable.
The exemplary embodiment will be explained in more detail with reference to the drawings.